Fig. 1. Self-assembly of laminin in neutral or acidic buffer. Frozen aliquots of laminin were dissolved in either Tris-HCl, pH 7 or in sodium acetate, pH 4, both containing 2 mM CaCl₂. Dilutions were made either in a pre-silanized cuvette (graphic) or in drops of buffer previously placed onto non-silanized coverslips (pictures). The graphic shows fluorescence spectra obtained for laminin in neutral (continuous line) and acidic buffer (dotted line) using excitation at 275 nm. The inset shows light-scattering intensity, using incidental light at 400 nm, for neutral (lower trace) and acidic condition (upper trace). Panels A to D show immunocytochemical analyses of laminin matrices formed on glass coverslips at pHs 7 (A,B) or 4 (C,D). Note that the apparent difference in the amount of bound protein in panels A and C is due to the impossibility of homogeneously focusing laminin aggregates throughout the neutral matrix. Insets show details of the corresponding main panels. Panels E to G show immunohistochemistry for laminin on whole-mount preparations of the retina of newborn rats (PO). A honeycomb pattern is typically seen on the periphery of the whole mount (E and F), whereas unorganized deposits characterize the center of the retina (G). The scale bars in panel A, main, and B correspond to 50 µm and apply to panels A, C and E or to panels B and D, respectively. The bar in the inset of panel A represents 10 µm and applies to all insets. In panel F, the bar corresponds to 100 µm in panels F and G.

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